Monolithic composite firewall

ABSTRACT

A ceramic fabric and a resin are combined to form a fire protection sheet capable of being co-cured onto a parent laminate structure. The resulting monolithic composite firewall shows fire protection ability comparable to that of the conventional titanium structure, without the problems associated therewith, such as titanium panel separation and disbonding. The fire protection sheet easily conforms to the shape of the parent laminate and is also useful as a repair material for damaged conventionally protected firewalls.

GOVERNMENT RIGHTS

[0001] This invention was first conceived or first built and tested inthe course of work under U.S. government contract number V22 ProgramN0019-85-C-0145. The government may have certain rights in thisinvention.

BACKGROUND OF THE INVENTION

[0002] The present invention generally relates to apparatus and methodsfor fireproofing and, more specifically, to apparatus and methods ofproviding a monolithic composite firewall in the canted deck of anaircraft.

[0003] Temperature and safety considerations bring out the need forfireproofing in a variety of applications. For example, the canted deckof the V22 Osprey aircraft has a fire protection requirement for thecabin roof below the mid-wing area below the auxiliary power unit (APU).

[0004] Referring to FIG. 3, there is shown a conventional configurationof the graphite panel from which the V-22 canted deck is constructed.Graphite panel 130 may be made of a plurality of graphite plies 140.Each graphite ply 140 may be bonded with an adjacent graphite ply 140 byany conventional means such as a commercially available resin.Preferably, graphite panel 130 contains from 4 to 12 graphite plies 140.More preferably, graphite panel 130 contains from 6 to 10 graphite plies140.

[0005] Referring to FIGS. 1-2, there is shown a conventional means forproviding fire protection in an aircraft canted deck. Fire protectionfor the V-22 canted deck 100 utilizes 0.012 in thick titanium panels 110which are mechanically fastened and bonded to the V-22's canted deck100. Titanium panels 110 are bonded at bond area 120 to the graphitepanel 130 which makes up the canted deck 100. Mechanical fasteners passthrough holes 122 in titanium panel 110 for mechanically securinggraphite panel 130 to titanium panel 110. The titanium panels 110require secondary bonding in addition to mechanical fastening in orderto be secured to the graphite laminate 130 of the canted deck 100. Overtime, the bond line between the titanium panels 110 and the canted deck100 becomes susceptible to dis-bonding, thus allowing fluids to migratebetween these two surfaces. This creates a potential safety issue as theintegrity of the firewall is reduced.

[0006] Conventional titanium panel firewalls have the furtherdisadvantage of increased fabrication complexity and manufacturing flowtime. Under current procedure, the titanium panels are manufactured andlocated on the canted deck. Pilot holes are drilled through the panelsand the canted deck skin. These holes are opened to full size and thepanel is disassembled. After cleaning/deburring/abrading the entranceand exit holes in the panel and canted deck skin, the panel isreassembled and bonded to the canted deck. Finally, mechanical fastenersare applied through the previously drilled holes to secure the titaniumpanel firewall to the canted deck. In addition, the manufacture oftitanium panel firewalls is made even more difficult when the parts arehighly contoured.

[0007] Conventional titanium panel firewalls have the additionaldisadvantage of high cost and weight. Providing adequate firewallprotection within a defined cost/weight parameter is an importantconsideration. Precision aircraft, such as the V-22 Osprey, havespecific specifications with respect to firewall durability and overallweight.

[0008] As can be seen, there is a need for an improved apparatus andmethod that provides an effective, durable, weight proportionatefirewall without the need for secondary bonding, mechanical fasteners orcomplex manufacturing steps.

SUMMARY OF THE INVENTION

[0009] In one aspect of the present invention, a firewall for a parentlaminate comprises a ceramic fabric; and a resin bonding the ceramicfabric to the parent laminate, the ceramic fabric and film adhesivebeing co-cured into the parent laminate to create the firewall.

[0010] In another aspect of the present invention, a monolithiccomposite firewall for a laminate surface comprises a ceramic fabric; aresin; the ceramic fabric impregnated with the resin to make a resinimpregnated ceramic fabric; and the resin impregnated ceramic fabricbeing co-cured with the laminate surface to form the monolithiccomposite firewall.

[0011] In a further aspect of the present invention, a monolithiccomposite firewall for a laminated deck of an aircraft comprises aceramic fabric capable of withstanding temperatures of about 2200° F.; aresin; the ceramic fabric impregnated with the resin to make a resinimpregnated ceramic fabric; and the resin impregnated ceramic fabricbeing co-cured with the laminated deck to form the monolithic compositefirewall.

[0012] In yet another aspect of the present invention, a method formaking a firewall material on a parent laminate, comprises impregnatinga ceramic fabric with a resin to form a firewall prepreg material; andco-curing the firewall prepreg material with the parent laminate to makethe firewall material.

[0013] In a still further aspect of the present invention, a method forproviding firewall protection on a laminated deck of an aircraft,comprises impregnating a ceramic fabric with a resin to form a firewallprepreg; the ceramic fabric includes continuous alumina-boria-silicafibers and is capable of withstanding temperatures of about 2200° F.;co-curing the firewall prepreg on the laminated deck to provide firewallprotection thereto.

[0014] These and other features, aspects and advantages of the presentinvention will become better understood with reference to the followingdrawings, description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a plan drawing showing the canted deck of the V22 Ospreyaircraft.

[0016]FIG. 2 is a perspective drawing showing a conventionalconfiguration for fire protection;

[0017]FIG. 3 is a perspective drawing showing a graphite panel having nofire protection;

[0018]FIG. 4 is a perspective drawing showing a fire protectionconfiguration according to an embodiment of the present invention;

[0019]FIG. 5 is a graph showing temperature measurements using aconventional configuration for fire protection;

[0020]FIG. 6 is a graph showing temperature measurements using a fireprotection configuration according to an embodiment of the presentinvention; and

[0021]FIG. 7 is a graph showing temperature measurements using agraphite laminate material without fire protection.

DETAILED DESCRIPTION OF THE INVENTION

[0022] The following detailed description is of the best currentlycontemplated modes of carrying out the invention. The description is notto be taken in a limiting sense, but is made merely for the purpose ofillustrating the general principles of the invention, since the scope ofthe invention is best defined by the appended claims.

[0023] The present invention generally provides a ceramic fabric andfilm adhesive which are combined to form a fire protection sheet capableof being co-cured onto a parent laminate structure. The resultingmonolithic composite firewall shows fire protection ability comparableto that of the conventional titanium structure, without the problemsassociated therewith. The fire protection sheet easily conforms to theshape of the parent laminate and is also useful as a repair material forconventionally protected firewalls. The present invention also providesa method of making such a monolithic composite firewall.

[0024] This is unlike the conventional firewall material in that thefirewall material of the present invention is a monolithic compositefirewall. Conventional firewall materials are formed as separate sheetsattached via a bonding material and mechanical fasteners to the parentlaminate. This conventional structure results in problems withdis-bonding, difficulties in manufacture, and high cost and weight. Themonolithic composite of the present invention solves these problems bystructurally incorporating the firewall as part of the parent laminateby co-curing bonding material for the individual parent laminate plieswith the bonding material of the firewall material.

[0025] While the embodiment below describes fire protection for agraphite laminate structure, the present invention is not intended to belimited thereto. The Nextel® fabric may be used as fire protection forbonding to any composite material such as graphite, carbon fiberreinforced plastic, fiberglass, thermoplastic, bismaleimide (BMI), andthe like.

[0026] The embodiment below describes the use of Nextel® fabric as fireproofing for the canted deck of an aircraft. However, the presentinvention is not limited to such use. The present invention may beapplicable where any material capable of being co-cured with the Nextel®fabric is in need of fire protection. For example, such a monolithiccomposite fire protection structure may be useful in furnaceapplications and the like.

[0027] Referring to FIG. 4, there is shown a fire protectionconfiguration according to an embodiment of the present invention. Thebonding for the individual plies of graphite panel 130 may be co-curedwith the resin bonding a sheet of Nextel® 312 (3M Corporation) fabric12. Nextel® 312 fabric 12 is composed or continuous polycrystallinemetal oxide fibers suitable for producing textiles without the aid ofother fiber or metal inserts. More specifically, Nextel® 312 is made of10-12 μm filaments having a 9Al₂O₃:2B₂O₃+amorphous SiO₂ crystal type.The composition of Nextel® 312 fabric is about 62 wt. % Al₂O₃, 24 wt. %SiO₂, and 14 wt. % B₂O₃.

[0028] The fabric 12 may be bonded to the graphite plies 140 bysandwiching the fabric 12 between two plies of film adhesive 14. CytecFM®-300 film adhesive may be used advantageously as the bondingmaterial. In this embodiment of the invention, the Cytec film adhesive14 is co-cured with the bonding for the graphite plies 140 to form themonolithic firewall material.

[0029] The fabric 12 may also be purchased in prepreg form as apre-impregnated fabric. The formation of a Nextel® 312 prepreg fabricmay be performed in any conventional resin prepreg-formation process.The pre-impregnated fabric may then be cut to the appropriate size andco-cured with the bonding for the graphite plies 140 to form themonolithic firewall material.

[0030] According to one feature of the present invention, the resin usedto bond graphite plies 140 may be the same as the resin used toimpregnate Nextel® fabric 12. While not limited to any particular resinsystem, FM®-300 and Metlbond® 1515 (Cytec Industries) are suitableresins for bonding both the graphite plies 140 to themselves and thefabric 12 to the graphite plies 140. Such a system removes the need forusing one resin to attach the firewall material to the graphite paneland a separate resin for making the graphite panel from its individualgraphite plies.

EXAMPLES

[0031] Referring back to FIG. 2, a conventional panel, hereinafterreferred to as “config 1”, was assembled by attaching, through bondingand mechanical fasteners, a 12 inch square titanium panel 110 to a 12inch square graphite panel 130. Bonding was applied to 1 to 2 inchperipheral bond area 120.

[0032] Referring now to FIG. 4, a fire protection configurationaccording to the present invention, hereinafter referred to as “config2”, was prepared by sandwiching one ply of Nextel® 312 fabric 12 between2 plies of film adhesive 14. Vacuum was applied for about 10 to 15minutes at 120° F. The resulting impregnated fabric is co-cured with theresin that bonds a plurality of graphite plies which make up graphitepanel 130.

[0033] Referring again to FIG. 3, a control panel was prepared bybonding eight 12 inch square graphite plies 140 to form graphite panel130. The resulting graphite panel 130 is hereinafter referred to as“config 3”.

[0034] Three panels from each of config 1, config 2, and config 3 weretested. Each panel was tested per BSS 7338 Propane Burner Test Method.More specifically, the test panels were exposed to a 2000° F. flame for15 minutes over a minimum area of 5 square inches with an average heatflux of 9.3 BTU/ft²·sec.

[0035] Referring to FIGS. 5-7, the temperature, recorded at the backsideof each panel, was recorded as a function of time. With the panelshaving fire protection (config 1 and config 2), the temperature wasrecorded 1 inch above the panel. With the graphite panel without fireprotection (config 3), the temperature was recorded 4 inches above thepanel. FIG. 5 represents one panel selected from the three tested forconfig 1, FIG. 6 represents one panel selected from the three tested forconfig 2, and FIG. 7 represents one panel selected from the three testedfor config 3.

[0036] Referring to FIG. 5 and 6, both the titanium and Nextel® panelspassed the flame penetration test. The backside temperatures of thetitanium and Nextel® configurations were approximately 300° F. by theend of the fifteen minute test.

[0037] Referring to FIG. 7, the unprotected graphite panels showed signsof burn through after about fourteen and a half minutes. As can be seenfrom the graph, the backside temperature reading is beginning to risestarting at about the 876 second mark. Therefore, the unprotectedgraphite panels failed the flame penetration test.

[0038] The titanium panels (config. 1) distorted and warped due to theextreme heat. The resin used to bond the titanium to the graphite wasburned off as well as most of the resin in the graphite. If the titaniumpanels were not mechanically fastened, they would have separated fromthe graphite portion of the panels.

[0039] The Nextel® fabric did not separate from the composite (config.2) and stayed in intimate contact with the graphite, even though most ofthe resin in the composite was burned off. Both the titanium (config. 1)and the Nextel® (config. 2) configurations are comparable for their fireproofing characteristics. However, the Nextel® configuration (config. 2)will reduce production cost and flow time in the manufacturing of thecanted deck. The Nextel® configuration (config. 2) also does not need tobe mechanically fastened to the canted deck. Therefore, there will notbe a knock down factor associated with the holes of config. 1 for thefasteners that secure the titanium. In other words, the overall bucklingstrength of the Nextel® configuration (config. 2) is not compromised bythe need to use mechanical fastener holes, as is the case in theconventional titanium configuration (config. 1). The Nextel®configuration (config. 2) should also reduce the weight compared to thatassociated with the conventional titanium fire protection (config. 1).

[0040] The ceramic fabric of the present invention may be used as arepair material in addition to the being used as an initial fireproofing material. Should burn through or removal of the existing fireprotection occur, the Nextel® fabric may be placed over and sufficientlyaround the burned through area. A film adhesive, such as Cytec FM™300brand film adhesive may be used to cure the fabric to the laminate.

[0041] It should be understood, of course, that the foregoing relates topreferred embodiments of the invention and that modifications may bemade without departing from the spirit and scope of the invention as setforth in the following claims.

We claim:
 1. A firewall for a parent laminate having a plurality ofindividual plies comprising: a ceramic fabric; a fabric resin bondingsaid ceramic fabric to said parent laminate; and a laminate resinbonding said plurality of individual plies, said fabric resin and saidlaminate resin being co-cured to create said firewall.
 2. The firewallaccording to claim 1, wherein said ceramic fabric includes continuousalumina-boria-silica fibers and is capable of withstanding temperaturesof about 2200° F.
 3. The firewall according to claim 1, wherein saidceramic fabric is made of 10-12 μm filaments having a9Al₂O₃:2B₂O₃+amorphous SiO₂ crystal type containing about 62 wt. %Al₂O₃, 24 wt. % SiO₂, and 14 wt. % B₂O₃.
 4. The firewall according toclaim 1, wherein said ceramic fabric is from about 5 to 15 mil thick. 5.The firewall according to claim 1, wherein said ceramic fabric is about10 mil thick.
 6. The firewall according to claim 1, wherein said ceramicfabric is pre-impregnated with said fabric resin.
 7. The firewallaccording to claim 1, wherein said fabric resin is a film adhesive. 8.The firewall according to claim 1, wherein said parent laminate is acanted deck of an aircraft.
 9. The firewall according to claim 1,wherein said plurality of individual plies comprises graphite layers.10. A monolithic composite firewall for a laminate comprising: a ceramicfabric; a fabric resin for bonding individual plies of said laminate; alaminate resin; said ceramic fabric impregnated with said fabric resinto make a resin impregnated ceramic fabric; and said resin impregnatedceramic fabric being co-cured with said laminate resin to form saidmonolithic composite firewall.
 11. The firewall according to claim 10,wherein said ceramic fabric includes continuous alumina-boria-silicafibers and is capable of withstanding temperatures of about 2200° F. 12.The firewall according to claim 10, wherein said ceramic fabric is madeof 10-12 μm filaments having a 9Al₂O₃:2B₂O₃+amorphous SiO₂ crystal typecontaining about 62 wt. % Al₂O₃, 24 wt. % SiO₂, and 14 wt. % B₂O₃. 13.The firewall according to claim 10, wherein said ceramic fabric is fromabout 5 to 15 mil thick.
 14. The firewall according to claim 10, whereinsaid ceramic fabric is about 10 mil thick.
 15. The firewall according toclaim 10, wherein said fabric resin is able to impregnate said fabricwhile being capable of co-curing with said laminate resin.
 16. Thefirewall according to claim 10, wherein said laminate is a canted deckof an aircraft.
 17. The firewall according to claim 10, wherein saidlaminate comprises a plurality of graphite layers.
 18. The firewallaccording to claim 17, wherein said fabric resin is the same as saidlaminate resin.
 19. A monolithic composite firewall for a laminated deckof an aircraft comprising: a ceramic fabric capable of withstandingtemperatures of about 2200° F.; a fabric resin; said ceramic fabricimpregnated with said fabric resin to make a resin impregnated ceramicfabric; a laminate resin for bonding the individual plies of saidlaminate deck; said resin impregnated ceramic fabric being co-cured withsaid laminated deck to form said monolithic composite firewall.
 20. Afireproof laminated deck comprising: a parent laminate comprising aplurality of individual laminate plies; a laminate resin bonding saidindividual plies; a ceramic fabric capable of withstanding temperaturesof about 2200° F.; and a fabric resin bonding said ceramic fabric withsaid individual plies, said fireproof laminated deck being formed whensaid laminate resin is co-cured with said fabric resin.
 21. Thefireproof laminated deck according to claim 20, wherein said individualplies are graphite plies.
 22. The fireproof laminated deck according toclaim 20, wherein said ceramic fabric is made of 10-12 μm filamentshaving a 9Al₂O₃:2B₂O₃+amorphous SiO₂ crystal type containing about 62wt. % Al₂O₃, 24 wt. % SiO₂, and 14 wt. % B₂O₃.
 23. The fireprooflaminated deck according to claim 20, wherein said laminate resin is thesame as said fabric resin.
 24. A method for making a firewall materialin a parent laminate having a plurality of individual plies, comprising:applying a laminate resin for bonding said individual plies;impregnating a ceramic fabric with a fabric resin to form a firewallprepreg material; co-curing said firewall prepreg material with saidlaminate resin to make said firewall material.
 25. The method for makinga firewall material according to claim 24, wherein said ceramic fabricincludes continuous alumina-boria-silica fibers and is capable ofwithstanding temperatures of about 2200° F.
 26. The method for making afirewall material according to claim 24, wherein said ceramic fabric ismade of 10-12 μm filaments having a 9Al₂O₃:2B₂O₃+amorphous SiO₂ crystaltype containing about 62 wt. % Al₂O₃, 24 wt. % SiO₂, and 14 wt. % B₂O₃.27. The method for making a firewall material according to claim 24,wherein said ceramic fabric is from about 5 to 15 mil thick.
 28. Themethod for making a firewall material according to claim 24, whereinsaid ceramic fabric is about 10 mil thick.
 29. The method for making afirewall material according to claim 24, further comprising choosing thesame resin material as said fabric resin and as said laminate resin.